Acrylonitrile polymer solutions



y 23, 1945- R. c. HOUTZ ACRYLONITRILE POLYMER SOLUTIONS Filed Nov. 4,1944 INVfiEfNTOR. BY 1 94 MM F.

ATTORNE Patented July 23, 1946 7 ACRYLONITRILE POLYMER SOLUTIONS BayClyde Bouts, Snyder, N.

du Pont de Nemours & Company,

Y., assignor to E. 1. Wilmington,

Deb, a corporation of Delaware Application November 4, 1944, Serial No.562,017

15 Claims. 1

This invention relates to a new composition of matter and shapedarticles produced therefrom. More particularly, this invention relatesto an organic solvent solution of polyacrylonitrile, i. e. polymerizedacrylonitrile or polymerized vinyl cyanide (CH:=CHCN) z, and copolymersand interpolymers of acrylonitrile in which at least 85% by weight ofthe polymer is acrylonitrile, and to the production of shaped articlesfrom said organic solvent solution of said polymers of acrylonitrile.

This application is a continuation-in-part of the copending applicationof Ray Clyde Houtz, Serial No. 447,446, filed June 17, 1942.

Polyacrylonitrile, and copolymers and interpolymers of acrylonitrilewith other'polymerizable substances, for example vinyl or acryliccompounds, in which at least 85% by weight of the polymer isacrylonitrile have been known for some time and recognized as possessingdesirable physical and chemical properties including toughness andinsolubllity in and insensitivity to common organic solvents such asmethyl or ethyl alcohol, acetone, ethyl ether, ethyl acetate,hydrocarbon solvents, chlorinated hydrocarbons and the like. Because ofthese facts, numerous attempts have been made to form these polymericmaterials into yarns, films and other shaped articles.

The copending application of George H. Latham, Serial No. 562,012, filedof even date herewith discloses solutions of polyacrylonitriie indimethyl carbamyl compounds and the production of extruded and otherwiseshaped articles and structures from such solutions. The abovesaidapplication of Geor e H. Latham represents the first successfuldissolution of polyacrylonitrile in a solvent to produce a solutionwhich is suitable for the production of commercially useful textileyarns or wrapping tissue films and similar tough. flexible structures.

The present application relates to a similarly satisfactory dissolutionof polyacrylonitrile in an organic solvent taken from a different classof organic compounds and the polyacrylonitrile solutions producedthereby are similarly satisfactory for the production of tough,flexible, dense, colorless yarns and films which are suitable for use inpractically all general commercial applications of such products.

It has been known heretofore that concentrated aqueous solutions ofinorganic salts such as lithium bromide, zinc chloride and sodiumsulfocyanide will dissolve polyacrylonltrile and it has been proposed(Rein U. S. Patent No. 2,140,921) to employ the resulting solutions inthe formation of yarns and films. However, it has been foundsubstantially impossible to use the resulting compositions in such amanner. Their extrusion into coagulating baths of the type proposed(including such non-solvents for acrylonitrlle as water, di-

2 lute acid, dilute salt solutions, etc.) result in the formation ofshaped articles that contain large amounts of the inorganic salt of theproposed solvent. These salts are distributed throughout the structureand destroy the continuity of the polyacrylonitrile phase and thestructure possesses poor physical properties, Removal of these salts,when possible, results in the formation of a porous, spongy, weak,undesirable structure that is very brittle and completely unsuited foruse as a yarn or film. Moreover, when it is attempted to form amultifllament yarn by extruding. for example the proposed aqueous sodiumsuli'ocyanide polyacrylonitrile composition, into a dilute acid bath, itis found that the individual filaments obtained stick together to forman essentially monofilament structure that is extremely brittle andcannot be bent or worked without breaking.

U. S. Patent No. 2,167,537 to Tobis points out that certain copolymersof acrylonitrile and an acrylic acid ester (those copolymers containingnot more than of acrylonltrile) are soluble in mixtures of organicsolvents such as dioxan, monochlorbenzene, cyclohexanone, etc. However,these liquids are incapable of dissolving or even swellingpolyacrylonitrile or copolymers of acrylonitrlle containing higherpercentages of acrylonitrile, i. e. acrylonitrile polymers of the typewith which this invention is concerned. As previously mentioned,polymers containing such high percentages (at least by weight) ofacrylonitrlle are especially desirable for use because of their goodphysical properties and excellent chemical resistance.

It has also been proposed (Rein U. S. Patent No. 2,117,210) to dissolvepolyacrylonltrile in molten quaternary ammonium salts such as benzylpyridiniurn chloride, an ionizable salt. Although the resulting solutioncan allegedly be used to form yams or films of polyacrylonitrile, thesolution itself is dark red to brown in color, indicating that somedecomposition of the polyacrylonitrile or some reaction between thepolyacrylonitrlle and the molten salt has probably taken place. Suchsolutions are not satisfactory for the production of commerciallyuseful, shaped articles of polyacrylonitrile. Here again, it has beenfound practically impossible to obtain iilamentary structures such asyarns from the composition. F'ilms or filaments, when obtainable, areextremely brittle; they are highly colored and very weak, presumablybecause of the presence within them of residual quaternary ammoniumsalt. Removal of this salt is difficult and the resulting structurescontain numerous and large voids that make the structures substantiallyuseless for commercial purposes.

It is therefore an object of this invention to dissolvepolyacrylonitrile or a copolymer or intel-polymer of acrylonitrile inwhich at least 85% by weight of the polymer is acrylonitrile, in asolvent which does not react with or decompose the polymer and which maybe substantially completely removed from the structures formed 01 such asolution.

It is another object of this invention to produce a solution ofpolyacrylonitrlle or a copolymer or interpolymer of acrylonitrile inwhich at least 85% by weight of the polymer is acrylonitrile, in asolvent which does not react with or decompose the polymer, the solutionbeing suitable for the formation of commercially useful, void freearticles of polyacrylonitrile, for example yarns which are suitable astextile yarns and films which are suitable as wrapping tissue.

It is another object oi this invention to produce a solution ofpolyacrylonitrile, or a copolymer or interpolymer of acrylonitrile inwhich at least 85% by weight of the polymer is acrylonitrile, in avolatile organic solvent, which solution is stable over extended periodsof time and is eminently suited for use in the manufacture of shapedarticles such as yarns, films, tubes, straws, artificial horsehair,bristles and ribbons, or when highly concentrated, for use in themanufacture of molded articles.

It is a still further object of this invention to produce shapedarticles and structures of polyacrylonitrile, or copolymers orinterpolymers of acrylonitrile in which at least 85% by weight of thepolymer is acrylonitrile.

It is still another object of thi invention to produce a shaped articleor structure of polyacrylonitrile or copolymers or interpolymers ofacrylonitrile in which at least 85% by weight of the polymer isacrylonitrile, for example a yarn, film, tube, bristle or the like whichis tough, flexible, tenacious and free from voids.

Other objects of the invention will appear hereinafter.

The objects of the invention may be accomplished in general bydissolving polyacrylonitrile, or a copolymer or interpolymer ofacrylonitrile in which at least 85% by weight of the polymer isacrylonitrile, in a. cyclic organic compound which is not a salt andwhich is fusible without decomposition composed of a single 3-8 memberedring containing within the ring the grouping:

wherein R represents H or and Z represents H: or 0, except that when Rrepresent H, Z must represent 0, not more than one of the ring membersbeing a bivalent chalcogen of atomic weight less than 33, the remainingring members (except the nitrogen shown in the above linkage) beingcarbon, said compound being otherwise free from side groups containingcarbon atoms; otherwise unsatisfied valences of the ring members beingsatisfied by hydrogen or by not more than one substituent taken from thegroup consisting of oxygen, bivalent sulfur, halogen, hydroxyl andthiol. (The term "chalcogen of atomic weight less than 33" is a termgenerally used to designate sulfur and oxygen.)

If the solvent has a relatively low boiling point (less than about 2500.), the solution of acrylonitrile polymer may then be formed into ashaped structure, for example a yarn or film, and the solvent removedfrom the shaped structure to coagulate the same. When the solvent isrelatively non-volatile and has a boiling point of about 300 C. or more,shaped articles may be made from the solution and at least a Portion ofthe solvent may be retained therein as a plasticizer for the articles.

It has been recognized in recent years that under certain conditions, anatom of hydrogen is attracted by rather strong forces to two atomsinstead of only one so that it may be considered to be acting as a bondbetween them. This is called the hydrogen bond.

The difliculty of dissolving polymer containing at least by weight ofacrylonitrile is due to the presence within the polymer molecules ofstrong hydrogen-bonding forces and in order to dissolve one of thesepolymers, it is necessary to find a material which will undergohydrogenbonding with the active hydrogen bonding groups of the polymermolecules and thus weaken the strong hydrogen bond within the polymermolecule and cause the hydrogen-bonding forces to be shared betweenmolecules of the polymer and the solvent. In this manner, it is possibleto form a molecular dispersion of the polymer within the solvent andthus form a solution.

However, the strength of the hydrogen bonding capacity cannot be takenas the sole criterion as to whether or not a compound will function todissolve an acrylonitrile polymer. It is also necessary that. in orderto function as a solvent for an aorylonitrile polymer, the compoundcontain certain groups which will be capable of satisfactorily sharing ahydrogen bonding force with the particular active group of theacrylonitrile polymer. In most instances, these groups require thepresence of a hydrogen atom on a, carbon atom to which the group isattached (designated as an alpha-hydrogen atom). Such groups as requirethe alpha-hydrogen atom are ineffective to impart solvent power if thealpha-hydrogen atom is missing.

It has now been found, in accordance with the present invention, thatthe 3-8 membered ring compounds having the particular structuredescribed above are found to have the proper degree of hydrogen bondingto enable them to dissolve the acrylonitrile polymers hereinabovereferred to.

Representative compounds coming within the scope of the above-mentionedtype of cyclic organic compounds and suitable for use as solvents forthe above-mentioned acrylonitrile polymers include:

B-hydroxy-2-plperidone O H lH-C bin-c 3-bydroxy-2-piporidone CHECKs-hydroxy-l pyrrolidone K0CH--CK:

rdm r-il-w m CK1CH;CH|C=O HICHQCHPNH Omega-hopiohctam Hg- H1N-i'ormylpiperidine CHICK,

C C=O OHr- H Alpha-piperidone CHr-CH,

Alpha-pyn'olidone CH -CH, 0

\JLH Hr-C! N-iormylpyrrolidine CHr-CHg-Cfh O H -CKg-CH:N-iormylhoxamethyleneimine CH -CH 0 0 N- H CHi-C| N-lormylmorpholineCHr-CHr-N-H C a C=0 CH;-CHQ

Epsilon-caprolactam CHr-N-H Ethylene carbamate CHzCHaClLCH: OH|CH:CHtN-CH NJonnylheptamethyleneimine CHI-CH! 0 BIG N-(JB CHI-CH!N-iormyl-i-bromopiporldine CHI-CHI 0 1-0 -PJ-H GH -C IN-icrmyl-l-iodopiperldine H-OH: 0 Cg: -E

CHI-CH1 N-iormylMhioropiperidine CHICK! o CH|O N-iormyl-l,MA-totrahydro-pyrldino 0 Hi C N-i'ormylthlomorphollne C H-C HI 0 H-C H:

N-iormyl-del te -p yrrollne Acrylonitrile polymer solutions formed bythe use of solvents embraced by the iormula set forth above are stableat room temperature (approximately 20 C.) and at temperaturesconsiderably above room temperature. Shaped structures and articles canbe produced by extruding man of such solutions into an evaporative orcoagulative medium. By forming the structures in an evaporative medium,the solvent must be evaporated therefrom and by forming the structuresin a coagulative medium, the solvent should be removed by selectivesolution in a non-solvent for the polymer.

The solutions are prepared by dissolving the polyacrylonitrile, orcopolymer or interpolymer oi. acrylonitrile with one or a mixture of theabovementioned solvents. Some of these solvents are solid at ordinarytemperatures and dissolve or retain the polymer in clear solution onlyat elevated temperatures, for example at temperatures of 100 C. orhigher, below which temperature the composition resembles a gel. In allcases when the polymer ls dissolved in a solvent or the above class, theresulting composition while hot has the appearance of a true solution.When cooled to room temperature, the composition generally takes on theappearance of a gel, which gel may, on standing, undergo syneresis.Reheating of this gel or syneresed mass however causes it to againreturn to solution form.

In view of the relatively high melting points of some of the solvents ofthis invention, they would have comparatively little use in theproduction of a polyacrylonitrile spinning or casting solution. Suchsolvents are however excellent solvent plasticizers forpolyacrylonitrile since they are soluhie in a wide range of proportionswith the said aorylonitrile polymers. The present invention thereforecontemplates solid solutions or acrylonitrile polymers containing atleast by weight of acrylonitrile as well as liquid solutions thereof.

Shaped articles obtained from solvent solutions oi polyacrylonitrile inaccordance with the invention and from which the solvent is subsequentlremoved are substantiall free of foreign matter and voids andsubstantially undecomposed 7 and chemically unchanged from the simplepolymer prior to its solution.

The above-described organic solvent solutions of acrylonitrile polymermay be shaped in the form or filaments, yarns, films, tubes and likestructures by apparatus and processes generally known in the art, thedetailed operating conditions being suitably modified.

Suitable methods and apparatus for the production of shaped articles ofthe polymers of this invention will be readily apparent by reference tothe following detailed description when taken in connection with theaccompanying illustrations in which:

Figure 1 is a diagrammatic vertical sectional view showing a dryspinning cell suitable for use in accordance with the invention;

Figure 2 is a diagrammatic perspective view showing a yarn drawingdevice for use in connection with the invention;

Figure 3 is a diagrammatic perspective view showing a wet spinningapparatus for use in the invention; and

Figure 4 is a diagrammatic side elevational view showing a suitable fllmcasting apparatus for use in accordance with the invention.

Referring to Figure 1 of the drawing, reference numeral H designates aspinneret through which a plurality of filaments ii are formed byextruding a filament forming solution supplied to the spinneret b meansof conduit I3. The spinning cell is jacketed with a material H such as arefractor in which is embedded an electrical heating coil IS. Thespinning cell can thus be operated at any desired temperature. Aplurality of conduits 2| are provided adjacent the bottom of the devicefor passing evaporative medium through the cell so as to evaporate thesolvent from the extruded filaments IS. The evaporative medium isremoved from the cell through outlet openings 23. The yarn comprisingthe plurality of filaments I5 is passed from the bottom of the spinningcell around guide roller 25 and is wound on a bobbin 21.

Referring to Figure 2 of the drawing. the yarn i5 is removed from thebobbin package 21 and passed about draw roller 29 and separating roller3L From draw roller 29, the yarn is passed to a second draw roller 33and separating roller 35. The yarn is passed around the two sets or drawrollers including their separating rollers a suflicient number of turnsto prevent slippage of the yarn. Draw roller 33 is rotated at a greaterspeed, for example three to ten times the speed of draw roller 20. Inthis manner, the yarn i 5 is stretched between the two draw rollers. Asthe yarn passes between the two draw rollers, a heating medium isbrought into contact with the yarn through blower nozzles 31 and 39. Theyarn passing from the draw roller 33 is wound on bobbin 4|. The drawingOr stretching of the spun yarn as described is not claimed as part ofthe present invention, but is claimed in the copendlng application ofDaniel T. Meloon, Serial No. 406,397, filed July 28, 1943.

Figure 3 or the drawing illustrates a, wet spinning apparatus i'or theproduction of yarn. The acrylonitrile polymer solution is passed throughconduit II and is extruded through spinneret 53 to form a multifilamentyarn 54. The yarn 54 is passed about guide roller 51 which is positionedwithin the coagulating liquid in tank 55. The yarn is then passed aboutguide roller 50 andis wound on bobbin ii.

The organic solvent solution 0! polyacrylonitrile may be cast in theform oi. a. film as illustrated in Figure 4. In accordance with thisapparatus, the polymer solution is passed from hopper H onto the endlesssteel band II where it is smoothed by means of a doctor knife 15. Theband, together with the film, is passed under a mean H for bringing a,heated drying medium into contact with the film. The film BI is pulledfrom the band 13 and collected on a mill roll 83.

The polyacrylonitrile for use with the invention is preferably preparedby the ammonium persulfate catalyzed polymerization oi monomericacrylonitrile dissolved or emulsified in water. It can. however, beprepared by any other suitable type of polymerization reaction such as,for example, the emulsion type reaction disclosed by U. 8. Patent No.2,160,054 to Bauer et al. The polymer preferably possesses a molecularweight within the range of 15,000 to 250,000 or even higher, acalculated from viscosity measurements by the Staudinger equation:

Molecular weight== C wherein: K,,,= 1.5 X 10- N =speoific viscosity= andThe molecular weight of the polymer obtained is dependent on suchfactors as the concentration of the monomer in the water, the amount andtype of catalyst present. the temperature of the reaction, etc. Forexample, polyaorylonitrile, having a molecular weight of approximately60,000 can be prepared as follows: To 94 pounds of distilled waterheated to 40 C. add 40 grams of ammonium per-sulfate catalyst and gramsof sodium bisulfite activator. Then add 16 pounds of acrylonitrile polywith stirring over a period of two hours. The polyacrylonitrile havingthe above said molecular weight will precipitate from the solution.Increasing or decreasing the amount of the catalyst, while maintainingthe other conditions constant, decreases or increases the molecularweight of the polymer. Acrylonitrile copolymers and interpolymerscontaining at least by weight of acrylonitriie and likewise preferablyhaving a molecular weight of 15,000 to 250,000 or higher can be preparedin a similar manner.

The following examples in which parts, proportions and pe centages areby weight unless otherwise specified illustrate preferred methods ofpreparing solutions in accordance with the principles of this inventionand of employing these solutions in the manufacture of commerciallysatisfactory shaped articles. The invention is not to be limited by thedetails set forth in the examples.

viscosity of solution viscosity of solvent -1 Emple I Fifteen (15) partsof an acrylonitrile polymer prepared by the polymerization of monomericacrylonitrile in accordance with the teachings of U. S. Patent No.2,160,054 to Bauer et a]. and possessing an average molecular weight of120,000 as determined by the Staudinger equation from viscosity datawere ground to an average particle size of 200 mesh and mixed with 85parts or N- formyl morpholine. Thi mixture was heated over a period ofthirty minutes to a temperature of C. to form a clear solution ng apyrollidine at room temperature viscosity of 100 poises at thistemperature. The solution was cast at a temperature or 120'- 0. onto apolished, metallic surface heated to a temperature of 150 C. to form athin. transparent film of the acrylonitrile polymer, the film beingtough, flexible and tear resistant.

Emmple II Fifteen parts of z (epsilon) caprolactam were added to asolution prepared by dissolving parts of the acrylonltrile polymer ofExample I in 80 parts of dimethyl formamide, the solution beingmaintained at a temperature of 50 C. The added material dissolvedreadily and the resulting clear solution was cast at a temperature of100 0. onto a polished, metallic surface heated to a temperature of 100C. to form a thin, transparent film of acrylonitrile polymer. The film,in addition to possessing the characteristic toughness of acryionitrilepolymer films, possesses a high durability and tear resistance. It washighly flexible. Analysis indicated that it possessed approximately ecaprolactam.

Example III Fifteen (15) parts of the finely divided pol mer of ExampleI were added to 85 parts of N-iormyl and the mixture heated to atemperature of 140 C. The resultin: clear solution was extruded at thistemperature through a 40-hole spinneret into a bath of trlethanolaminemaintained at a temperature of 110 C. to form a multifilament yarnhaving a denier of 160. The yarn was passed through the bath for a totaldistance of 30 inches and was subjected during its travel to a tensionof 0.5 gram per denier. The yarn was collected on a bobbin at a speed of2,000 inches per minute and was washed and dried on the bobbin. Itpossessed a tenacity or 3.5 grams per denier and an elongation of 15%,

As indicated in the above examples, it is possible by the practice ofthis invention to obtain a solution of polyacrylonitrile, or a copolymeror interpolymer of acrylonitrlle which is eminently suited for use inthemanufacture of shaped articles such as yarns, films, or moldedarticles. These solutions are also suited for use as lacquers or coatingcompositions. They are especially useful in the coating of wire andelectrical parts where the high chemical and electrical resistance ofthe polymer is important.

For the purpose of definition, a solvent is a material which, when inthe liquid state. is capable of forming solutions in which the polymeris present in a concentration by weight of 5% or more. In mostinstances, the polymer is soluble in almost all proportions although themiscibility may take place at elevated temperatures in the case ofcertain compounds.

As also shown, the solvents of the invention are useful not only inconnection with the polyacrylonitrile, but also with copolymers andinterpolymers of acrylonitrile with other polymerizable substances suchas, for example, compounds containing one or more ethylenic linkagesincluding vinyl and acrylic compounds as well as olefinic or clioleflnichydrocarbons, such as isobutylene. butadiene, etc. They are eminentlysatisfactory for use with these polymers that contain an aP- preciableamount of acrylonitrile, for example polymers, copolymers andinterpolymers that contain at least 85% by weight of acrylonitrile andthat have generally been regarded by the art as being completelyinsoluble in all common organic solvents. Nor are these solvents limitedto use with a polyacrylonitrile of any given molecular weight. They canbe used with a. polymer of almost any given molecular weight and areespecially satisfactory for use with those polymers having an averagemolecular weight within the range 15,000 to 250,000 as determined byviscosity data using the Staudinger equation and intended for use in themanufacture of yarns or films.

The solution of acrylonitrile polymer dissolved in an organic solvent inaccordance with this invention must be of such a. concentration that itsviscosity at the operating temperature is within a workable range. Whenit is to be employed in the spinning of yarn or the casting of film, thesolution should preferably have a viscosity within the range of 25 to750 pulses. When the polymer has a molecular weight of 250,000 or more,this requires that the maximum concentration of polymer in the spinningsolution be of the order of 10%. Generally. it is preferred that thespinning solution contain at least 10% of the polymer because of thedifficulty of rapidly removing large amounts of solvent from thesolution in the spinning operation. Moreover, it is economicallyundesirable to use such large amounts of solvent for the spinning of a.given amount of polymer although it is true that th solvent can becompletely recovered from t e spinning operation and reused. For thesereasons, it is preferred to employ a polymer having an average molecularweight of between 40,000 and 150,000 since such a polymer forms asolution of the desired viscosity in concentrations of the order of 15%to 25%, and at a desirable spinning temperature of the order of to C. Ofcourse, it is within the scope of the invention to heat the solution toa higher temperature. even to above the normal boiling point of thesolvent, for the actual spinning operation. Here again, the controllingfactor with regard to the temperature of the spinning solution is theviscosity of the solution.

The evaporative medium employed in the dry spinning of filaments andyarns or the dry castin; of films in accordance with this invention maybe any vapor inert to the filmor filamentforming solution such as air,nitrogen, steam, etc. or any suitable mixture thereof. The temperatureof the evaporative medium is dependent on such factors as the dimensionsof the spinning cell, the composition and rate of extrusion of thespinning solution and the rate of flow of the evaporative medium. It isonly necessary that these several factors be so correlated that the yarnor other shaped article leaving the spinning cellbe sufiiciently freedof the solvent so that it is solidified and capable of being wound intopackage form or otherwise collected.

As indicated in Example III above, shaped articles of acrylonitrilepolymer can also be formed by extruding the spinning solution into asuitable precipitating bath comprising a. liquid that is miscible withthe solvent but is a. chemically inert non-solvent for the acrylonitrilepolymer. As examples of such a liquid may be mentioned water, glycerin,organic solvents such as alcohol, ether, etc., or aqueous solutions ofsalts, aikalies or acids. The copending application of William W.Watkins, Serial No. 496,376, filed July 28, 1943, covers the use ofglycerol, triethanolamine and aqueous solutions of salts, as baths,preferably at elevated temperatures, for the wet spinning ofacrylonitrile polymer yarn, from solutions of the polymer, preferablywith substantial tension and stretch being applied during spinnins.

The article of acylonitrile polymer thus obtained can advantageously besubjected to a stretching operation of the type employed in the aboveexamples. This stretching is preferably performed by passing the yarnbetween two positively driven rollers, the peripheral speeds of whichare so adjusted that the article is stretched to from two to ten timesits original length, preferably approximately six times its originallength. This stretching of the formed article may be performed at anysuitable time. However, in the case of articles formed by the wetspinning or casting technique, it is preferably performed before thearticle has been completely dried. The orientation of the structure thusobtained greatly improved the physical properties of the structureincluding its tenacity, its resilience, etc.

In addition to acting as solvents for polyacrylonitrile, or copolymersor interpolymers oi acrylonitrile, the cyclic compounds of thisinvention, when present in small amounts, can also be used aslasticizing agents for the polymer and the higher boiling compounds ofthe invention are especially suited for such use. At the same time, itis, of course, to be understood that non-solvent softeners such asglycerol can also be incorporated in the solutions of this invention,these materials remaining in the subsequently formed articles to imparta softening effect. If it is desired to use such plasticizing orsoftening agents with polyacrylonitrile, they are preferably added inthe desired amount to an already formed solution of the polymer in alower boiling solvent, for example to a. solution of the polymer inN-formyl pyrollidine.

This invention is primarily concerned with the steps of dissolvingpolyacrylonitrile in a suitable solvent to form a stable solutionadapted for use in the manufacture of shaped articles ofpolyacrylonitrile. It is characteristic of the invention that thesolutions provided by it are stable: the solvents do not cause adecomposition or chemical alteration of the dissolved acrylonitrilepolymer. At the same time, it is also characteristic that the solventsprovided by the invention are also useful in the dissolving of mixturesoi polyacrylonitrile and adjuvants such as dye modifiers, linearpolyamides such as nylon. derivatives of cellulose including celluloseethers and esters, polymers of vinyl compounds such as vinyl chloride,vinyl acetate, acrylic acid, etc., which adiuvants may be incorporatedin the acrylonitrile polymer solution to modify the properties, bothchemical and physical, of the resulting shaped articles.

This invention provides a. class of solvents for polyacrylonitrile, andcopolymers and interpolymers of acrylonitrile which were heretoforeconsidered substantially insoluble. The solvents are capable of formingwith the polymer clear solutions that are stable for extended periods oftime at both room and elevated temperatures and are admirably suited foruse as lacquers or coating compositions or in the manufacture of shapedarticles of the polymer, for example by extrusion into an evaporative orcoagulative medium, or by the use of a molding technique.

The invention also rovides a class of materials that is eminently suitedfor use in plasticizing structures comprising the acrylonitrilepolymers. The materials provided by this invention are apparently truesolvents for the above-mentioned acrylonitrile polymers. They do nottend to re act with or decompose the polymer, the polymeric 1 materialobtained from the solution of this invention apparently being of thesame identical chemical composition as the initial polymer.

Yarns, films and similar articles of polyacrylonitrile prepared from thesolutions of this invention can be stretched to yield orientedstructures that possess a high tenacity, a desirable elongation and ahigh elastic recovery that compares favorably with that of silk. Thearticles are not contaminated with undesirable salts and they aresubstantially free of void spaces.

Reference, throughout the specification and. claims, to acrylonitrilepolymers, polymers of acrylonitrile, and copolymers and interpolymers ofacrylonitrile "containing at least by weight of acrylonitrile signifiespolymers con taining in their molecules at least 85% by weight of theacrylonitrile unit which is considered to be resent in the polymermolecule as the group that is, at least 85% by weight of the reactantmaterial converted into and forming the polymer is acrylonitrile.

Since it is obvious that many changes and modifications can be made inthe above described details without departing from the nature and spiritof the invention, it is to be understood that the invention is not to belimited to the details described herein except as set forth in theappended claims.

I claim:

1. A a new composition of matter, a polymer of acrylonitrile containingin the polymer molecule at least 85% by weight of acrylontrile dissolvedin a cyclic organic compound composed of a singe 3-8 membered ringcontaining within the ring the grouping:

wherein R represents and Z represents a member of the class consistingof H: and 0. not more than one of the ring members being a bivalentchalcogen of atomic weight less than 33, the remaining ring membersbeing carbon, said compound being otherwise free from side groupcontaining carbon atoms; otherwise unsatisfied valences of the ringmembers being satisfied by hydrogen and not more than one substituenttaken from the group consisting of oxygen, bivalent sulfur, halogen,hydroxyl and thiol.

2. As a new composition of matter as defined in claim 1, in which thepolymer of acrylonitrile is polyacrylonitrile.

3. A a new composition of matter as defined in claim 1, in which saidcyclic compound is nonreactive with said polymer.

4. As a new composition of matter as defined in claim 1, in which thecyclic compound is nonreactive with said polymer but is soluble in allproportions therewith.

5. As a new composition of matter as defined in claim 1, in which thepolymer of acrylonitrile has a molecular weight of between 15,000 and250,000.

6. As a new composition of matter as defined 13 in claim 1, in which thepolymer of acrylonitrile hes a molecular weight of between 40,000 and150,000.

'1. As a new composition oi matter as defined in claim 1. in which saidcyclic organic compound is N-iormyl pyrrolidine.

8. As a new composition of matter as defined in claim 1, in which saidcyclic organic compound is N-iormyl morpholine.

9. As a new composition of matter, a polymer of acrylonitrile containingin the polymer molecule at least 85% by weisht of acrylonitrile and acyclic organic compound composed of a single 3-8 membered r1 8containing within the ring the N-B l wherein R represents and Zrepresents a member or the class consisting or H: and 0, not more thanone 01' thering members being bivalent chalcogen of atomic weight lessthan 33, the remaining ring memhers being carbon, said compound beingotherwise tree from side groups containing carbon atoms; otherwiseunsatisfied valences oi the ring members being satisfied by hydrogen andnot more than one substituent taken from the group consisting of oxygen,bivalent sulfur, halogen, hydroxyl and thiol.

10. The composition of claim 1 in which the solution contains at least10% of said polymer of acrylonitrile.

11. The composition as defined in claim 1 m which the polymer ofacrylonitrile is polyacrylonitride and said cyclic organic compound isN-iormyl pyrrolidine.

12. The composition as defined in claim 1 in which the polymer ofacrylonitrile is p yacrylonitrile and said cyclic organic compound is N-fonnyl morpholine.

13. The composition as defined in claim 1 in which the polymer ofacrylonitrile is polyacrylonitrile having a molecular weight or! between15,000 and 250,000.

14. The composition as defined in claim 1 in which the polymer ofacrylonitrile is polyacrylonitrile having a molecular weight oi between40,000 and 150,000.

15. The composition of claim 1 in which the solution ha a viscositywithin the range 25 to 750 poises.

RAY CLYDE HOUTZ.

Certificate of Correction Patent No. 2,404,719.

July 23, 1940.

RAY CLYDE HOUTZ numbered patent requi read represents; column 4, ines72to 74, and column the formula reading column 12, line 37 claimi, forshould be read with of the case in the Patent Ofiice.

Signed and sealed this 5th day of November,

printed specification of the above line 62, for represent 5, lines 1 to3, for that portion of mad Hs sings read single; and that the saidLetters Paten these corrections therein that the same may coniorm to therecord LESLIE FRAZER,

First 4m'strmt Uommissz'omr of Patents.

13 in claim 1, in which the polymer of acrylonitrile hes a molecularweight of between 40,000 and 150,000.

'1. As a new composition oi matter as defined in claim 1. in which saidcyclic organic compound is N-iormyl pyrrolidine.

8. As a new composition of matter as defined in claim 1, in which saidcyclic organic compound is N-iormyl morpholine.

9. As a new composition of matter, a polymer of acrylonitrile containingin the polymer molecule at least 85% by weisht of acrylonitrile and acyclic organic compound composed of a single 3-8 membered r1 8containing within the ring the N-B l wherein R represents and Zrepresents a member or the class consisting or H: and 0, not more thanone 01' thering members being bivalent chalcogen of atomic weight lessthan 33, the remaining ring memhers being carbon, said compound beingotherwise tree from side groups containing carbon atoms; otherwiseunsatisfied valences oi the ring members being satisfied by hydrogen andnot more than one substituent taken from the group consisting of oxygen,bivalent sulfur, halogen, hydroxyl and thiol.

10. The composition of claim 1 in which the solution contains at least10% of said polymer of acrylonitrile.

11. The composition as defined in claim 1 m which the polymer ofacrylonitrile is polyacrylonitride and said cyclic organic compound isN-iormyl pyrrolidine.

12. The composition as defined in claim 1 in which the polymer ofacrylonitrile is p yacrylonitrile and said cyclic organic compound is N-fonnyl morpholine.

13. The composition as defined in claim 1 in which the polymer ofacrylonitrile is polyacrylonitrile having a molecular weight or! between15,000 and 250,000.

14. The composition as defined in claim 1 in which the polymer ofacrylonitrile is polyacrylonitrile having a molecular weight oi between40,000 and 150,000.

15. The composition of claim 1 in which the solution ha a viscositywithin the range 25 to 750 poises.

RAY CLYDE HOUTZ.

Certificate of Correction Patent No. 2,404,719.

July 23, 1940.

RAY CLYDE HOUTZ numbered patent requi read represents; column 4, ines72to 74, and column the formula reading column 12, line 37 claimi, forshould be read with of the case in the Patent Ofiice.

Signed and sealed this 5th day of November,

printed specification of the above line 62, for represent 5, lines 1 to3, for that portion of mad Hs sings read single; and that the saidLetters Paten these corrections therein that the same may coniorm to therecord LESLIE FRAZER,

First 4m'strmt Uommissz'omr of Patents.

